The distribution of boiling (liquid) cryogens, such as liquid nitrogen, is problematic due to the parasitic heat load provided by a cryosurgical device's plumbing or transport circuit, which is maintained at ambient temperature. Pre-cooling the plumbing circuit, even if adequately insulated, causes two-phase flow (liquid-gas mixtures), cryogen boil-off, and choking flow due to gas expansion in the transport circuit. As a result, target temperatures at the distal end of the flow path (i.e., cryoprobe tip) are not reached for many minutes.
Some prior cryogenic systems and devices are disclosed in U.S. Pat. No. 4,345,598 to Zobac et al.; U.S. Pat. No. 4,472,946 to Zwick; U.S. Pat. No. 4,860,545 to Zwick et al.; U.S. Pat. No. 4,946,460 to Merry et al.; U.S. Pat. No. 5,254,116 to Baust et al.; U.S. Pat. No. 5,257,977 to Eshel; U.S. Pat. No. 5,334,181 to Rubinsky et al.; U.S. Pat. No. 5,400,602 to Chang et al.; U.S. Pat. No. 5,573,532 to Chang et al.; and U.S. Pat. No. 5,916,212 to Baust et al., the entire contents of each being hereby incorporated herein by reference thereto, respectively.